Host and viral determinants of airborne transmission of SARS-CoV-2 in the Syrian hamster.

It remains poorly understood how SARS-CoV-2 infection influences the physiological host factors important for aerosol transmission. We assessed breathing pattern, exhaled droplets, and infectious virus after infection with Alpha and Delta variants of concern (VOC) in the Syrian hamster. Both VOCs displayed a confined window of detectable airborne virus (24-48 hr), shorter than compared to oropharyngeal swabs. The loss of airborne shedding was linked to airway constriction resulting in a decrease of fine aerosols (1-10 µm) produced, which are suspected to be the major driver of airborne transmission. Male sex was associated with increased viral replication and virus shedding in the air. Next, we compared the transmission efficiency of both variants and found no significant differences. Transmission efficiency varied mostly among donors, 0-100% (including a superspreading event), and aerosol transmission over multiple chain links was representative of natural heterogeneity of exposure dose and downstream viral kinetics. Co-infection with VOCs only occurred when both viruses were shed by the same donor during an increased exposure timeframe (24-48 hr). This highlights that assessment of host and virus factors resulting in a differential exhaled particle profile is critical for understanding airborne transmission.

Compartmentalized SARS-CoV-2 replication in upper versus lower respiratory tract after intranasal inoculation or aerosol exposure.

Non-human primate models are essential for the development of vaccines and antivirals against infectious diseases. Rhesus macaques are a widely utilized infection model for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We compared cellular tropism and virus replication in rhesus macaques inoculated with SARS-CoV-2 via the intranasal route, or via exposure to aerosols. Intranasal inoculation results in replication in the upper respiratory tract and limited lower respiratory tract involvement, whereas exposure to aerosols results in infection throughout the respiratory tract. In comparison to multi-route inoculation, the intranasal and aerosol inoculation routes result in reduced SARS-CoV-2 replication in the respiratory tract.

Environmental Persistence and Disinfection of Lassa Virus.

Lassa fever, caused by Lassa virus (LASV), is endemic to West Africa, where ≈300,000 illnesses and ≈5,000 deaths occur annually. LASV is primarily spread by infected multimammate rats via urine and fomites, highlighting the need to understand the environmental fate of LASV. We evaluated persistence of LASV Josiah and Sauerwald strains on surfaces, in aqueous solutions, and with sodium hypochlorite disinfection. Tested strains were more stable in deionized water (first-order rate constant [k] for Josiah, 0.23 days; for Sauerwald, k = 0.34 days) than primary influent wastewater (Josiah, k = 1.3 days; Sauerwald, k = 1.9 days). Both strains had similar decay rates on high-density polyethylene (Josiah, k = 4.3 days; Sauerwald, k = 2.3 days) and stainless steel (Josiah, k = 5.3 days; Sauerwald, k = 2.7 days). Sodium hypochlorite was highly effective at inactivating both strains. Our findings can inform future risk assessment and management efforts for Lassa fever.

Stability of Monkeypox Virus in Body Fluids and Wastewater.

An outbreak of human mpox infection in nonendemic countries appears to have been driven largely by transmission through body fluids or skin-to-skin contact during sexual activity. We evaluated the stability of monkeypox virus (MPXV) in different environments and specific body fluids and tested the effectiveness of decontamination methodologies. MPXV decayed faster at higher temperatures, and rates varied considerably depending on the medium in which virus was suspended, both in solution and on surfaces. More proteinaceous fluids supported greater persistence. Chlorination was an effective decontamination technique, but only at higher concentrations. Wastewater was more difficult to decontaminate than plain deionized water; testing for infectious MPXV could be a helpful addition to PCR-based wastewater surveillance when high levels of viral DNA are detected. Our findings suggest that, because virus stability is sufficient to support environmental MPXV transmission in healthcare settings, exposure and dose-response will be limiting factors for those transmission routes.

Comparative Aerosol and Surface Stability of SARS-CoV-2 Variants of Concern.

SARS-CoV-2 transmits principally by air; contact and fomite transmission may also occur. Variants of concern are more transmissible than ancestral SARS-CoV-2. We found indications of possible increased aerosol and surface stability for early variants of concern, but not for the Delta and Omicron variants. Stability changes are unlikely to explain increased transmissibility.

Host and viral determinants of airborne transmission of SARS-CoV-2 in the Syrian hamster.

It remains poorly understood how SARS-CoV-2 infection influences the physiological host factors important for aerosol transmission. We assessed breathing pattern, exhaled droplets, and infectious virus after infection with Alpha and Delta variants of concern (VOC) in the Syrian hamster. Both VOCs displayed a confined window of detectable airborne virus (24-48 h), shorter than compared to oropharyngeal swabs. The loss of airborne shedding was linked to airway constriction resulting in a decrease of fine aerosols (1-10µm) produced, which are suspected to be the major driver of airborne transmission. Male sex was associated with increased viral replication and virus shedding in the air. Next, we compared the transmission efficiency of both variants and found no significant differences. Transmission efficiency varied mostly among donors, 0-100% (including a superspreading event), and aerosol transmission over multiple chain links was representative of natural heterogeneity of exposure dose and downstream viral kinetics. Co-infection with VOCs only occurred when both viruses were shed by the same donor during an increased exposure timeframe (24-48 h). This highlights that assessment of host and virus factors resulting in a differential exhaled particle profile is critical for understanding airborne transmission.

Comparative aerosol and surface stability of SARS-CoV-2 Variants of Concern.

SARS-CoV-2 is transmitted principally via air; contact and fomite transmission may also occur. Variants-of-concern (VOCs) are more transmissible than ancestral SARS-CoV-2. We find that early VOCs show greater aerosol and surface stability than the early WA1 strain, but Delta and Omicron do not. Stability changes do not explain increased transmissibility.

Evaluation of Five Buffers for Inactivation of Monkeypox Virus and Feasibility of Virus Detection Using the Panther Fusion® Open Access System.

Rapid diagnosis is key to containing viral outbreaks. However, for the current monkeypox outbreak the major deterrent to rapid testing is the requirement for higher biocontainment of potentially infectious monkeypox virus specimens. The current CDC guidelines require the DNA extraction process before PCR amplification to be performed under biosafety level 3 unless vaccinated personnel are performing assays. This increases the turn-around time and makes certain laboratories insufficiently equipped to handle specimens from patients with suspected monkeypox infection. We investigated the ability of five commercially available lysis buffers and heat for inactivation of monkeypox virus. We also optimized the use of monkeypox virus in Hologic® Panther Specimen Lysis Buffer for detection of virus in the Panther Fusion® Open Access System using published generic and clade specific monkeypox virus primers and probes.

ChAdOx1 nCoV-19 (AZD1222) or nCoV-19-Beta (AZD2816) protect Syrian hamsters against Beta Delta and Omicron variants.

ChAdOx1 nCoV-19 (AZD1222) is a replication-deficient simian adenovirus-vectored vaccine encoding the spike (S) protein of SARS-CoV-2, based on the first published full-length sequence (Wuhan-1). AZD1222 has been shown to have 74% vaccine efficacy against symptomatic disease in clinical trials. However, variants of concern (VoCs) have been detected, with substitutions that are associated with a reduction in virus neutralizing antibody titer. Updating vaccines to include S proteins of VoCs may be beneficial, even though current real-world data is suggesting good efficacy following boosting with vaccines encoding the ancestral S protein. Using the Syrian hamster model, we evaluate the effect of a single dose of AZD2816, encoding the S protein of the Beta VoC, and efficacy of AZD1222/AZD2816 as a heterologous primary series against challenge with the Beta or Delta variant. Minimal to no viral sgRNA could be detected in lungs of vaccinated animals obtained at 3- or 5- days post inoculation, in contrast to lungs of control animals. In Omicron-challenged hamsters, a single dose of AZD2816 or AZD1222 reduced virus shedding. Thus, these vaccination regimens are protective against the Beta, Delta, and Omicron VoCs in the hamster model.

UV-C Light Completely Blocks Aerosol Transmission of Highly Contagious SARS-CoV-2 Variants WA1 and Delta in Hamsters.

Behavioral and medical control measures have not been effective in containing the spread of SARS-CoV-2 in large part due to the unwillingness of populations to adhere to "best practices". Ultraviolet light with wavelengths of between 200 and 280 nm (UV-C) and, in particular, germicidal ultraviolet light, which refers to wavelengths around 254 nm, have the potential to unobtrusively reduce the risk of SARS-CoV-2 transmission in enclosed spaces. We investigated the effectiveness of a strategy using UV-C light to prevent airborne transmission of the virus in a hamster model. Treatment of environmental air with 254 nm UV-C light prevented transmission of SARS-CoV-2 between individuals in a model using highly susceptible Syrian golden hamsters. The prevention of transmission of SARS-CoV-2 in a natural system by treating elements of the surrounding environment is one more weapon in the arsenal to combat COVID. The results presented indicate that coupling mitigation strategies utilizing UV-C light, along with current methods to reduce transmission risk, have the potential to allow a return to normal indoor activities.

Zaire ebolavirus surveillance near the Bikoro region of the Democratic Republic of the Congo during the 2018 outbreak reveals presence of seropositive bats.

On the 8th of May, 2018, an outbreak of Ebola virus disease (EVD) was declared, originating in the Bikoro region of the Democratic Republic of the Congo (DRC) near the border with neighboring Republic of the Congo (ROC). Frequent trade and migration occur between DRC and ROC-based communities residing along the Congo River. In June 2018, a field team was deployed to determine whether Zaire ebolavirus (Ebola virus (EBOV)) was contemporaneously circulating in local bats at the human-animal interface in ROC near the Bikoro EVD outbreak. Samples were collected from bats in the Cuvette and Likouala departments, ROC, bordering the Équateur Province in DRC where the Bikoro EVD outbreak was first detected. EBOV genomic material was not detected in bat-derived samples by targeted quantitative reverse transcription-polymerase chain reaction or by family-level consensus polymerase chain reaction; however, serological data suggests recent exposure to EBOV in bats in the region. We collected serum from 144 bats in the Cuvette department with 6.9% seropositivity against the EBOV glycoprotein and 14.3% seropositivity for serum collected from 27 fruit bats and one Molossinae in the Likouala department. We conclude that proactive investment in longitudinal sampling for filoviruses at the human-animal interface, coupled with ecological investigations are needed to identify EBOV wildlife reservoirs.

OraSure InteliSwab™ Rapid Antigen Test Performance with the SARS-CoV-2 Variants of Concern-Alpha, Beta, Gamma, Delta, and Omicron.

The emergence of SARS-CoV-2 in the human population and the resulting COVID-19 pandemic have led to the development of various diagnostic tests. The OraSure InteliSwab™ COVID-19 Rapid Test is a recently developed and FDA emergency use-authorized rapid antigen-detecting test that functions as a lateral flow device targeting the nucleocapsid protein. Due to SARS-CoV-2 evolution, there is a need to evaluate the sensitivity of rapid antigen-detecting tests for new variants, especially variants of concern such as Omicron. In this study, the sensitivity of the OraSure InteliSwab™ Test was investigated using cultured strains of the known variants of concern (VOCs, Alpha, Beta, Gamma, Delta, and Omicron) and the ancestral lineage (lineage A). Based on dilution series in cell culture medium, an approximate limit of detection for each variant was determined. The OraSure InteliSwab™ Test showed an overall comparable performance using recombinant nucleocapsid protein and different cultured variants, with recorded limits of detection ranging between 3.77 × 105 and 9.13 × 105 RNA copies/mL. Finally, the sensitivity was evaluated using oropharyngeal swabs from Syrian golden hamsters inoculated with the six VOCs. Ultimately, the OraSure InteliSwab™ COVID-19 Rapid Test showed no decrease in sensitivity between the ancestral SARS-CoV-2 strain and any VOCs including Omicron.

Efficacy of ChAdOx1 vaccines against SARS-CoV-2 Variants of Concern Beta, Delta and Omicron in the Syrian hamster model.

ChAdOx1 nCoV-19 (AZD1222) is a replication-deficient simian adenovirusâ€"vectored vaccine encoding the spike (S) protein of SARS-CoV-2, based on the first published full-length sequence (Wuhan-1). AZD1222 was shown to have 74% vaccine efficacy (VE) against symptomatic disease in clinical trials and over 2.5 billion doses of vaccine have been released for worldwide use. However, SARS-CoV-2 continues to circulate and consequently, variants of concern (VoCs) have been detected, with substitutions in the S protein that are associated with a reduction in virus neutralizing antibody titer. Updating vaccines to include S proteins of VoCs may be beneficial over boosting with vaccines encoding the ancestral S protein, even though current real-world data is suggesting good efficacy against hospitalization and death following boosting with vaccines encoding the ancestral S protein. Using the Syrian hamster model, we evaluated the effect of a single dose of AZD2816, encoding the S protein of the Beta VoC, and efficacy of AZD1222/AZD2816 as a heterologous primary series against challenge with the Beta or Delta variant. We then investigated the efficacy of a single dose of AZD2816 or AZD1222 against the Omicron VoC. As seen previously, minimal to no viral sgRNA could be detected in lungs of vaccinated animals obtained at 5 days post inoculation, in contrast to lungs of control animals. Thus, these vaccination regimens are protective against the Beta, Delta, and Omicron VoCs in the hamster model.

OraSure InteliSwab ® Rapid Antigen Test performance with the SARS-CoV-2 Variants of Concern Alpha, Beta, Gamma, Delta, and Omicron.

The emergence of SARS-CoV-2 in the human population and the resulting COVID-19 pandemic has led to the development of various diagnostic tests. The OraSure InteliSwab ® COVID-19 Rapid Test is a recently developed and FDA emergency use authorized rapid antigen-detecting test that functions as a lateral flow device targeting the nucleocapsid protein. Due to SARS-CoV-2 evolution, there is a need to evaluate the sensitivity of rapid antigen-detecting tests for new variants, especially variants of concern like Omicron. In this study, the sensitivity of the OraSure InteliSwab ® Test was investigated using cultured strains of the known variants of concern (VOCs, Alpha, Beta, Gamma, Delta, and Omicron) and the ancestral lineage (lineage A). Based on dilution series in cell culture medium, an approximate limit of detection for each variant was determined. The OraSure InteliSwab ® Test showed an overall comparable performance using recombinant nucleocapsid protein and different cultured variants with recorded limits of detection ranging between 3.77 × 10 5 and 9.13 × 10 5 RNA copies/mL. Finally, the sensitivity was evaluated using oropharyngeal swabs from Syrian golden hamsters inoculated with the 6 VOCs. Ultimately, the OraSure InteliSwab ® COVID-19 Rapid Test showed no decrease in sensitivity between the ancestral SARS-CoV-2 strain and any VOCs including Omicron.

Increased small particle aerosol transmission of B.1.1.7 compared with SARS-CoV-2 lineage A in vivo.

The major transmission route for SARS-CoV-2 is airborne. However, previous studies could not elucidate the contribution between large droplets and aerosol transmission of SARS-CoV-2 and its variants. Here, we designed and validated an optimized transmission caging setup, which allows for the assessment of aerosol transmission efficiency at various distances. At a distance of 2 m, only particles of <5 µm traversed between cages. Using this setup, we investigated the relative efficiency of aerosol transmission between the SARS-CoV-2 Alpha variant (B.1.1.7) and lineage A in Syrian hamsters. Aerosol transmission of both variants was confirmed in all sentinels after 24 h of exposure as demonstrated by respiratory virus shedding and seroconversion. Productive transmission also occurred after 1 h of exposure, highlighting the efficiency of this transmission route. Interestingly, after donors were infected with a mix of both variants, the Alpha variant outcompeted the lineage A variant in an airborne transmission chain. Overall, these data indicate that a lower infectious dose of the Alpha variant, compared to lineage A, could be sufficient for successful transmission. This highlights the continuous need to assess emerging variants and the development for pre-emptive transmission mitigation strategies.

UV-C light completely blocks highly contagious Delta SARS-CoV-2 aerosol transmission in hamsters.

Behavioral and medical control measures are not effective in containing the spread of SARS-CoV-2. Here we report on the effectiveness of a preemptive environmental strategy using UV-C light to prevent airborne transmission of the virus in a hamster model and show that UV-C exposure completely prevents airborne transmission between individuals.

Sodium hypochlorite disinfection of SARS-CoV-2 spiked in water and municipal wastewater.

Infectious severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has the potential to be collected in wastewater from mucus, sputum, and feces of infected individuals, raising questions about the appropriate handling and treatment of the resulting wastewater. Current evidence indicates the likelihood of waterborne SARS-CoV-2 transmission is low; nonetheless, confirming the efficacy of disinfection against SARS-CoV-2 is prudent to ensure multiple barriers of protection for infectious SARS-CoV-2 that could be present in municipal and hospital wastewater. Sodium hypochlorite (free chlorine) is widely used for pathogen control in water disinfection applications. In the current study, we investigated the inactivation of SARS-CoV-2 in DI water and municipal wastewater primary influent by sodium hypochlorite (free chlorine) addition. Our results showed rapid disinfection of SARS-CoV-2, with less than 1 mg-min/L required for >3 log10 TCID50 reduction in DI water. More than 5 mg-min/L was required for 3 log10 TCID50 reduction in primary influent, suggesting potential shielding of the virus by suspended solids. These results are consistent with expected virus inactivation by free chlorine and suggest the adequacy of free chlorine disinfection for inactivation of infectious SARS-CoV-2 in water matrices.

Surface‒Aerosol Stability and Pathogenicity of Diverse Middle East Respiratory Syndrome Coronavirus Strains, 2012‒2018.

Middle East respiratory syndrome coronavirus (MERS-CoV) infects humans and dromedary camels and is responsible for an ongoing outbreak of severe respiratory illness in humans in the Middle East. Although some mutations found in camel-derived MERS-CoV strains have been characterized, most natural variation found across MERS-CoV isolates remains unstudied. We report on the environmental stability, replication kinetics, and pathogenicity of several diverse isolates of MERS-CoV, as well as isolates of severe acute respiratory syndrome coronavirus 2, to serve as a basis of comparison with other stability studies. Although most MERS-CoV isolates had similar stability and pathogenicity in our experiments, the camel-derived isolate C/KSA/13 had reduced surface stability, and another camel isolate, C/BF/15, had reduced pathogenicity in a small animal model. These results suggest that although betacoronaviruses might have similar environmental stability profiles, individual variation can influence this phenotype, underscoring the need for continual global viral surveillance.

ChAdOx1 nCoV-19 (AZD1222) protects Syrian hamsters against SARS-CoV-2 B.1.351 and B.1.1.7.

We investigated ChAdOx1 nCoV-19 (AZD1222) vaccine efficacy against SARS-CoV-2 variants of concern (VOCs) B.1.1.7 and B.1.351 in Syrian hamsters. We previously showed protection against SARS-CoV-2 disease and pneumonia in hamsters vaccinated with a single dose of ChAdOx1 nCoV-19. Here, we observe a 9.5-fold reduction of virus neutralizing antibody titer in vaccinated hamster sera against B.1.351 compared to B.1.1.7. Vaccinated hamsters challenged with B.1.1.7 or B.1.351 do not lose weight compared to control animals. In contrast to control animals, the lungs of vaccinated animals do not show any gross lesions. Minimal to no viral subgenomic RNA (sgRNA) and no infectious virus can be detected in lungs of vaccinated animals. Histopathological evaluation shows extensive pulmonary pathology caused by B.1.1.7 or B.1.351 replication in the control animals, but none in the vaccinated animals. These data demonstrate the effectiveness of the ChAdOx1 nCoV-19 vaccine against clinical disease caused by B.1.1.7 or B.1.351 VOCs.

Immunogenicity of Low-Dose Prime-Boost Vaccination of mRNA Vaccine CV07050101 in Non-Human Primates.

Many different vaccine candidates against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the etiological agent of COVID-19, are currently approved and under development. Vaccine platforms vary from mRNA vaccines to viral-vectored vaccines, and several candidates have been shown to produce humoral and cellular responses in small animal models, non-human primates, and human volunteers. In this study, six non-human primates received a prime-boost intramuscular vaccination with 4 µg of mRNA vaccine candidate CV07050101, which encodes a pre-fusion stabilized spike (S) protein of SARS-CoV-2. Boost vaccination was performed 28 days post prime vaccination. As a control, six animals were similarly injected with PBS. Humoral and cellular immune responses were investigated at time of vaccination, and two weeks afterwards. No antibodies could be detected at two and four weeks after prime vaccination. Two weeks after boost vaccination, binding but no neutralizing antibodies were detected in four out of six non-human primates. SARS-CoV-2 S protein-specific T cell responses were detected in these four animals. In conclusion, prime-boost vaccination with 4 µg of vaccine candidate CV07050101 resulted in limited immune responses in four out of six non-human primates.